This invention relates to adjustable width rolls for a rolling mill, and more particularly to adjustable width rolls particularly suitable for horizontal rolls of a universal mill used for producing H-beams or the like.
In order to produce H-beams by rolling, universal mills are generally used, in which a pair of horizontal rolls arranged above and below and a pair of vertical rolls arranged on both sides are incorporated in the same roll stand.
In the case that H-beams are produced by the use of such a rolling mill, widths of flanges of H-beams can be freely changed so long as the widths of the flanges are within widths of vertical rolls. On the other hand, as web heights h of the H-beams are determined by thicknesses t.sub.1 of the flanges and widths W of the horizontal rolls reSulting from a relation h=W+2t.sub.1, there are the following difficulties concerning the web heights.
The expression "width of roll or roll width" used herein is intended to mean a barrel length of a roll which directly contacts a product to be rolled.
1) End surfaces of the horizontal rolls perform reduction and rolling of inner surfaces of H-beams so that wear occurs at the end surfaces to a great extent. Therefore, the heights of the H-beams tend to reduce even in one rolling procedure as rolled amounts are increased, so that rolled products having a constant size cannot be stably obtained. It is therefore required to frequently exchange the rolls in order to produce rolled products of a constant size. PA1 2) Although the widths of the flanges of H-beams can be freely selected, the heights of webs are limited to only one size per one pair of horizontal rolls. PA1 3) With H-beams having a constant height h, there are many flange thiCkneSses t.sub.1 in the relation h=W+2t.sub.1 under one nominal size. Therefore, it is needed to change the widths W of the horizontal rolls dependent upon required thicknesses t.sub.1 so that the horizontal rolls must frequently be exchanged to meet the requirements of thicknesses. As a result, the productivity is detrimentally affected and the number of man-hours are increased. PA1 4) The end surfaces of the horizontal rolls must be frequently machined to make the roll widths W of the horizontal rolls coincident with inner sizes W.sub.1 in order to improve the accuracy in size. Therefore, the cost per one roll is increased (FIG. 5).
In order to solve the above problems, there have been many proposals. For example, Japanese Patent Applications Laid-open Nos. 61-262,407 and 61-169,105 proposed features of inserting spacers for adjusting roll widths between a pair of sleeve rolls to compensate for the wear of rolls (FIG. 1). Moreover, Japanese Patent Application Laid-open No. 61-262,407 disclosed a feature of moving sleeve rolls in their axial directions relative to their centers with the aid of screws and nuts threadedly engaging with each other to adjust widths of the rolls. Furthermore, Japanese Patent Applications Laid-open Nos. 59-202,101; 61-172,605; and 63-56,302 proposed features of using rolls obliquely moving to freely change heights of webs of H-beams.
In the system using the spacers inserted between the sleeve rolls, the horizontal rolls must be removed from a roll stand in an off-line for the purpose of inserting the spacers into or removing from the sleeve rolls. These operations detrimentally affect the production efficiency, and the number of man-hours for mounting and dismounting is increased. What is worse still, fine adjustment of roll widths is difficult in this system.
In the system moving the sleeve rolls in their axial directions, complicated means for driving the sleeve rolls is required and the rigidity of the sleeve rolls in transverse directions becomes lower. Moreover, when rolling load is applied, horizontal rolls wobble in their axial directions, so that rolled products are inferior in dimensional accuracy.
In the system using the rolls obliquely movable, installations for this purpose are greatly complicated to prohibitively increase the initial cost.